Bacterial growth

The measurement of an exponential bacterial growth curve in batch culture was traditionally a part of the training of all microbiologists; the basic means requires bacterial enumeration (cell counting) by direct and individual (microscopic, flow cytometry[1]), direct and bulk (biomass), indirect and individual (colony counting), or indirect and bulk (most probable number, turbidity, nutrient uptake) methods.

It emphasizes clonality, asexual binary division, the short development time relative to replication itself, the seemingly low death rate, the need to move from a dormant state to a reproductive state or to condition the media, and finally, the tendency of lab adapted strains to exhaust their nutrients.

The cells do not reproduce in synchrony without explicit and continual prompting (as in experiments with stalked bacteria [9]) and their exponential phase growth is often not ever a constant rate, but instead a slowly decaying rate, a constant stochastic response to pressures both to reproduce and to go dormant in the face of declining nutrient concentrations and increasing waste concentrations.

[1] Near the end of the logarithmic phase of a batch culture, competence for natural genetic transformation may be induced, as in Bacillus subtilis[10] and in other bacteria.

When Escherichia coli is growing very slowly with a doubling time of 16 hours in a chemostat most cells have a single chromosome.

Spatially structured environments such as biofilms or agar surfaces present additional complex growth models.

It's been proven that after death phase E. coli can be maintained in batch culture for long periods without adding nutrients.

[13] Environmental factors influence rate of bacterial growth such as acidity (pH), temperature, water activity, macro and micro nutrients, oxygen levels, and toxins.

Low temperatures tend to reduce growth rates which has led to refrigeration being instrumental in food preservation.

This article includes material from an article posted on 26 April 2003 on Nupedia; written by Nagina Parmar; reviewed and approved by the Biology group; editor, Gaytha Langlois; lead reviewer, Gaytha Langlois; lead copyeditors, Ruth Ifcher.